U.S. patent application number 12/764075 was filed with the patent office on 2011-10-20 for output controllable frequency modulation electronic ballast.
Invention is credited to CHIEN-CHIH KUO.
Application Number | 20110254458 12/764075 |
Document ID | / |
Family ID | 44787734 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110254458 |
Kind Code |
A1 |
KUO; CHIEN-CHIH |
October 20, 2011 |
OUTPUT CONTROLLABLE FREQUENCY MODULATION ELECTRONIC BALLAST
Abstract
An output controllable frequency modulation electronic ballast
includes a first stage for converting AC current into DC current
and boosting of voltage; a buck DC-DC converter; a transistor of
the buck DC-DC converter having an input end which is selected from
a gate for MOSFET and a base for a bipolar transistor; and a PWM
controller connected between the input end of the buck DC-DC
converter and an output end of the lamp body; a frequency
controllable oscillator being connected to the PWM controller for
providing variable frequency to the PWM controller as a base band
signals of the PWM controller; and an oscillation controlling
processor being connected to the frequency controller oscillator
for generating instructions to change the oscillation frequency of
the frequency controller oscillator and thus to adjust the
modulation frequency of the output of the PWM controller.
Inventors: |
KUO; CHIEN-CHIH; (Taipei
City, TW) |
Family ID: |
44787734 |
Appl. No.: |
12/764075 |
Filed: |
April 20, 2010 |
Current U.S.
Class: |
315/224 |
Current CPC
Class: |
H05B 41/3927 20130101;
H05B 41/2883 20130101; H05B 41/3925 20130101 |
Class at
Publication: |
315/224 |
International
Class: |
H05B 41/36 20060101
H05B041/36 |
Claims
1. An output controllable frequency modulation electronic ballast,
in that an output frequency of a buck DC-DC converter is adjustable
for changing pulse widths and duty cycles of voltage and current
pulses from an output of the buck DC-DC converter to an lamp body
so as to adjust illumination of the lamp body; the ballast
comprising: a first stage for converting AC current into DC current
and boosting of voltage; a buck DC-DC converter; a transistor of
the buck DC-DC converter having an input end which is selected from
a gate for MOSFET and a base for a bipolar transistor; and a PWM
controller connected between the input end of the buck DC-DC
converter and an output end of the lamp body; a frequency
controllable oscillator being connected to the PWM controller for
providing variable frequency to the PWM controller as a base band
signals of the PWM controller; and an oscillation controlling
processor being connected to the frequency controller oscillator
for generating instructions to change the oscillation frequency of
the frequency controller oscillator and thus to adjust the
modulation frequency of the output of the PWM controller.
2. The output controllable frequency modulation electronic ballast
as claimed in claim 1, wherein the frequency controllable
oscillator is formed by an electronic oscillator and an adjusting
circuit; the electronic oscillator is an oscillation circuit formed
by electronic elements; and the adjusting circuit includes at least
one resistor and at least one capacitor; and at least one switch is
used to switch the resistor and the capacitor so as to form with
different assembly of the at least resistor and the at least one
capacitor for adjusting the frequency of the electronic
oscillator.
3. The output controllable frequency modulation electronic ballast
as claimed in claim 2, wherein the adjusting circuit is formed by
connecting respective ends of a plurality of capacitors to the
electronic oscillator; another ends of these capacitors being
connected to one end of a capacitor switch in parallel; another end
of the capacitor switch being connected to one end of a resistor;
and another end of the resistor being connected to another end of
the electronic oscillator; wherein by switching the capacitor
switch, only one of the capacitors is connected to the
resistor.
4. The output controllable frequency modulation electronic ballast
as claimed in claim 2, wherein the adjusting circuit is formed by
connecting one end of the electronic oscillator to one end of a
capacitor; another end of the capacitor being further connected to
one end of a resistor switch; another end of the resistor switch
being connected to respective ends of a plurality of resistors
which are arranged in parallel; another ends of the resistors being
connected to another end of the electronic oscillator.
5. The output controllable frequency modulation electronic ballast
as claimed in claim 2, wherein the adjusting circuit is formed by
connecting one end of the electronic oscillator to a capacitor
switch; the capacitor switch being further connected to respective
ends of a plurality of capacitors; the capacitor switch cause that
only one of the capacitors being conducted, while other capacitors
are disconnected in the circuit; another ends of the capacitors
being further connected to one end of a resistor switch in
parallel; another end of the resistor switch being connected to a
plurality of resistors; the resistors being connected to another
end of the electronic oscillator; and the resistor switch causes
that only one of the resistors is conducted, while other resistors
are not conducted; thus the combinations of the capacitors and the
resistors generate many different oscillation frequencies to be
provided by the electronic oscillator.
6. The output controllable frequency modulation electronic ballast
as claimed in claim 3, wherein the capacitor switch is connected to
the oscillation controlling processor; and the oscillation
controlling processor is built with a frequency control software
which includes the logics for controlling the switching of the
capacitor switch based on a desired effect of the lamp.
7. The output controllable frequency modulation electronic ballast
as claimed in claim 4, wherein the resistor switch is connected to
the oscillation controlling processor; and the oscillation
controlling processor is built with a frequency control software
which includes the logics for controlling the switching of the
resistor switch based on a desired effect of the lamp.
8. The output controllable frequency modulation electronic ballast
as claimed in claim 5, wherein the capacitor switch and the
resistor switch are connected to the oscillation controlling
processor; and the oscillation controlling processor is built with
a frequency control software which includes the logics for
controlling the switching of the capacitor switch and the resistor
switch based on a desired effect of the lamp.
9. The output controllable frequency modulation electronic ballast
as claimed in claim 1, wherein the frequency controllable
oscillator is a quartz oscillator and a frequency controller; the
quartz oscillator outputs a signal of fixed frequency which is
further input to the frequency controller; the frequency controller
inputs the fixed frequency signal from the quartz oscillator and
output another signal with a desired frequency; the frequency
controller is connected to the oscillation controlling processor;
the frequency controller is connected to the PWM controller.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to lamps, and in particular to
an output controllable frequency modulation electronic ballast, in
that an output frequency of a buck DC-DC converter is adjustable
for changing pulse widths and duty cycles of voltage and current
pulses from an output of the buck DC-DC converter to an lamp body
so as to adjust illumination of the lamp body;
BACKGROUND OF THE INVENTION
[0002] With reference to FIG. 1, the relation of the voltage with
respect to time of the actuation of an HID lamp is illustrated. In
FIG. 2, the relation of the current with respect to time of the
actuation of the HID lamp is illustrated. When the HID lamp is
actuated, the internal gas will convert to a form of plasma. The
voltage between two electrodes of the lamp tube will operate with a
specific range. When the HID lamp is steady, the light efficiency
of the HID lamp is controlled by adjusting the current, while the
variation of the voltage between the two electrodes is small.
[0003] The power sources of the HID lamps may be AC source or DC
source. After an HID lamp is light up, to sustain the temperature
between the two electrodes, if the temperature of the electrodes
descends too quickly, the electrons cannot be stimulated. Then the
HID lamp will distinguish.
[0004] To control the HID lamp lights efficiency is to adjust the
input current of the HID lamp. Generally, an HID lamp is an
intrinsic light efficiency. The control process is that to actuate
the HID lamp with a normal light efficiency. After the HID lamp is
steady, the input current is adjusted to control the light
efficiency of the HID lamp.
[0005] However, this control way needs to change the structure of
the ballast of the HID lamp, while this is inconvenient.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to provide a lamp
control system by controlling the buck DC-DC converter.
Furthermore, sensors about voltages, currents, illuminations are
installed for light strength control, temperature control,
auto-turning on and off of the HID lamp, power control and time and
illumination control.
[0007] To achieve above object, the present invention provides an
output controllable frequency modulation electronic ballast, in
that an output frequency of a buck DC-DC converter is adjustable
for changing pulse widths and duty cycles of voltage and current
pulses from an output of the buck DC-DC converter to an lamp body
so as to adjust illumination of the lamp body; the ballast
comprising: a first stage for converting AC current into DC current
and boosting of voltage; a buck DC-DC converter; a transistor of
the buck DC-DC converter having an input end which is selected from
a gate for MOSFET and a base for a bipolar transistor; and a PWM
controller connected between the input end of the buck DC-DC
converter and an output end of the lamp body; a frequency
controllable oscillator being connected to the PWM controller for
providing variable frequency to the PWM controller as a base band
signals of the PWM controller; and an oscillation controlling
processor being connected to the frequency controller oscillator
for generating instructions to change the oscillation frequency of
the frequency controller oscillator and thus to adjust the
modulation frequency of the output of the PWM controller.
[0008] The various objects and advantages of the present invention
will be more readily understood from the following detailed
description when read in conjunction with the appended drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows the relationship of the HID lamp actuation
voltage versus time.
[0010] FIG. 2 shows the relationship of the HID lamp actuation
current versus time.
[0011] FIGS. 3-1 and 3-2 show the functional block of an HID
ballast, where FIG. 3-1 is suitable for an AC HID lamp and FIG. 3-2
shows a DC HID lamp.
[0012] FIG. 4 is a simple circuit for a buck DC-DC converter.
[0013] FIG. 5 shows a circuit, where a buck DC-DC converter is
serially connected to a PWM controller and an oscillator is used to
provide base band signals to the PWM controller.
[0014] FIG. 6 shows the current states of the elements in FIG.
5.
[0015] FIG. 7 shows the current states for the elements in FIG.
5.
[0016] FIG. 8 is a flow diagram for a PWM controller to control the
buck DC-DC converter.
[0017] FIG. 9 shows the relationship of PWM control with a fixed
load.
[0018] FIG. 10 shows the relation of PWM control with a reduced
load.
[0019] FIG. 11 shows the relationship of PWM control with an
enlarged load.
[0020] FIG. 12 shows the relationship of current versus time, where
the PWM control outputs a predetermined frequency.
[0021] FIG. 13 shows the relationship of current versus time, where
the output frequency of the PWM control is two time of that in FIG.
12.
[0022] FIG. 14 shows that a frequency controllable oscillator and
an oscillation controlling process are added to the PWM
controller.
[0023] FIG. 15 shows the first operation mode for controlling the
output of the buck DC-DC converter.
[0024] FIG. 16 shows the second operation mode for controlling the
output of the buck DC-DC converter.
[0025] FIG. 17 shows the third operation mode for controlling the
output of the buck DC-DC converter.
[0026] FIG. 18 shows another way for adjustment of frequency of the
present invention, wherein the frequency controllable oscillator is
a quartz oscillator added with a frequency controller 401.
DETAILED DESCRIPTION OF THE INVENTION
[0027] In order that those skilled in the art can further
understand the present invention, a description will be provided in
the following in details. However, these descriptions and the
appended drawings are only used to cause those skilled in the art
to understand the objects, features, and characteristics of the
present invention, but not to be used to confine the scope and
spirit of the present invention defined in the appended claims.
[0028] The structure of the present invention will be described
herein with reference to the attached drawings. The present
invention is suitable for AC or DC driving lamps. However, in the
following the AC driving HID lamp is used in the description of the
invention, while this is only a preferred embodiment, but it is not
used to confine the scope of the present invention.
[0029] With reference to FIGS. 3-1 and 3-2, the internal structure
of an HID ballast if illustrated. The structure in FIG. 3-1 is
suitable for AC driving HID lamp. FIG. 3-2 shows a DC driving HID
lamp. Since most HID lamp is driven by AC signal, general public
power source has voltages between 110 to 240V which can not be
provide to HID lamps. Thus the voltage adjust ballasts are
necessary.
[0030] Generally, the basic structure of an electronic ballast has
three main sections.
[0031] A first stage is a rectified voltage boost PFC control stage
(AC to DC control). At this stage, AC current is converted into DC
current and the voltage is boosted based on the actuating voltage
of the HID lamp and an igniter circuit. As illustrated in FIG. 1,
in a classic embodiment, this stage has an EMI (electromagnetic
interference) filter, a rectifier, and a voltage booster PFC for
promoting conversion efficiency from AC to DC. A rear end of the
ballast has an igniter for providing a transient high voltage. Thus
other than conversion from AC to DC, a front end of the ballast has
a voltage booster for providing boosting voltage to the
igniter.
[0032] A second stage is a buck DC-DC converter for conversion low
DC voltage to high DC voltage so as to control the light efficiency
of the HID lamp. The conversion of DC to DC is mainly the control
of current. The lighting efficiency of the HID lamp is controlled
by current. Actuation of HID lamp needs high voltage. When the HID
lamp enters into a steady operation, the driving voltage is farther
lower than the voltage in actuation. Thus, the output voltage of
the buck DC-DC converter in the second stage is variable. Since in
steady state, the controlling the HID lamp is mainly by current, a
current controlling buck DC-DC converter is used at this stage.
[0033] A third stage is AC HID lamp full bridge output control (DC
to AC) and an igniter for converting DC to AC to drive the HID
lamp. If the HID lamp is DC driving, only the igniter is used. The
current and voltage of the HID lamp is controlled by the second
stage.
[0034] FIG. 4 shows a simple circuit model of the buck DC-DC
converter. The buck DC-DC converter includes a transistor Q1 (such
as a bipolar transistor or a field effect transistor), which is
used as a power switch. A current I enters into an input end of the
transistor. The output end of the transistor includes an LRC
circuit for adjusting the current and the voltage. In this example,
the LRC current includes a series connected diode D1, and an
inductor L1 connected to the diode D1. An output end of the
inductor is further connected to a capacitor C1 and a load resistor
RL. The charging and discharging of the capacitor and the inductor
are controlled by switching the transistor Q1 so as to have the
effect of voltage boosting. Generally, the output current and
voltage are feedback to the input end so as to switch the
transistor periodically and thus to control the duty cycle of pulse
output from the transistor. Thus the voltage is controlled.
[0035] With reference to FIG. 5, it is illustrated that a PWM
(pulse width modulation) controller is serially connected between
the buck DC-DC converter and the transistor Q1 for controlling the
switching signal from PWM controller to the transistor so as to
control the output power. An oscillator serves to provide a base
band signal to the PWM controller. The PWM controller receives the
feedback signal from the load end so as to modulate the pulse width
in the PWM controller. The output of the PWM controller is
transferred to the buck DC-DC converter as a working signal. The
duration of the pulse width will control the charge and discharge
time period of the capacitor and the inductor so as to change the
voltage, current and power at the output end. Thus the illumination
of the HID lamp is controlled.
[0036] Referring to FIGS. 6 and 7, the current states of the
elements in FIG. 5 are shown. The duty cycle at the output signal
of the PWM controller is controlled by the voltage difference,
current or power at the output end of the buck DC-DC converter
(since the light property of the HID lamp is driven by current).
The output current is detected by a current sensor. In the drawing,
Iu represents the current passing through the inductor L1. V1 shows
the state at the input end of the inductor L1, that is, the
switching state of transistor Q1.
[0037] When transistor Q1 conducts, the input current of the V1
point will flow through the inductor L1. The output current will
increase. When the current increase to a limit value, the
transistor Q1 will be turned off. Then the energy stored in the
inductor L1 will supply to the output end. Then the output current
decreases. When the current decreases a low limit, the transistor
Q1 conducts again so make the L1 to store energy. This cycle
performs repeatedly to sustain the operation of the circuit.
[0038] Since the lighting property of the HID lamp is based on the
driving current. In lighting, the voltage varies continuously
within a great range. The feedback control of the buck DC-DC
converter can be achieved by the following way.
[0039] In the buck DC-DC converter, the switching of the transistor
Q1 is based on the setting of the current operation range. The
feedback control of the current is for protecting the output
current of the circuit from overloading and thus the load is not
burnt out. The minimum of the current is based on the driving
frequency so as to prevent insufficiency of power supply.
[0040] The factors about the feedback control of the buck DC-DC
converter are the loading R1, the inductance of the inductor L1,
the capacitance of the capacitor C1, the permissible current range,
and the permissible voltage range, etc.
[0041] In the following, a brief description about the current
feedback control is described.
[0042] In FIG. 5, it is illustrated that a PWM controller is added
with an oscillator. The frequency of the PWM controller is
generated by the oscillator. Then the current Iu is detected, the
PWM controller outputs pulse width modulation signal based on the
Iu.
[0043] FIG. 8 shows the flow diagram about the PWM signal for
controlling the transistor Q1. The operation will be described
herein. In that an oscillation signal is sent. The system detects
whether it is a positive trigger (step 1001). If no, the process
repeats. If yes, the system determine whether the current is
greater than an upper limiter (step 1002), If Q1 is turned off and
the process returns to the step 1001. If yes, Q1 will be turned on
(step 1003) and then the system detects whether the current is
greater than an upper limit, if no the process repeats. If Q1 turns
off and the process returns to step 1001.
[0044] FIGS. 9 to 11 are schematic views about the control of the
PWM control. In FIG. 9, it shows that the load is fixed. The
relation between the PWM output voltage and the output current Io
of the buck DC-DC converter is illustrated. In FIG. 10, it shows
that the duty cycle becomes smaller than 50%. The charge time of
the capacitor C1 is shortened and the discharge time is prolonged.
In FIG. 11, it shows that the duty cycle becomes greater than 50%.
The charge time of the capacitor C1 is prolonged and the discharge
time is shortened.
[0045] FIGS. 12 and 13 shows that the load, current limit,
capacitor, and inductor are not changed. The duty cycle of the PWM
controller is changed. The effect to the buck DC-DC converter 502
is illustrated. In FIG. 12, it shows that the load is fixed. In
FIG. 13, the output frequency of the PWM controller is doubled. It
is illustrated that the current level (Io) is higher.
[0046] The HID lamp is driven by current. When current becomes
large, the power of the HID lamp becomes large. The PWM can
effectively control the illumination of the HID lamp.
[0047] The present invention provides a structure to change the
lighting efficiency of the HID lamp by controlling the baseband
frequency of the PWM controller. The change of the baseband
frequency of the PWM controller will change the duty cycle of the
PWM signal so as to change the charging and discharging time period
of the inductor L1 and the capacitor C1.
[0048] The way for controlling the PWM baseband signal according to
the present invention will be described herein.
[0049] Referring to FIG. 14, a frequency controllable oscillator
200 is connected to the PWM controller for providing variable
frequency to the PWM controller and an oscillation controlling
processor 300 is connected to the frequency controller oscillator
200 for generating instructions to change the oscillation frequency
of the frequency controller oscillator 200 and thus to adjust the
modulation frequency of the output of the PWM controller.
[0050] See FIG. 14, in the present invention, the frequency
controllable oscillator 200 is formed by an electronic oscillator
200 and an adjusting circuit. The electronic oscillator 210 is an
LC (L: inductor; C: capacitor) oscillation circuit, that is: a
manual made oscillator by electronic elements. The arrangement will
be described here.
[0051] At this stage, the electronic oscillator 210 is connected
with an adjusting circuit which includes at least one capacitors
and at least one resistors.
[0052] There are three forms of the adjusting circuits.
[0053] The first way is illustrated in FIG. 15, the adjusting
circuit includes respective ends of a plurality of capacitors C0 to
C4. Another ends of these capacitors are connected to one end of a
capacitor switch SW1 in parallel. Another end of the capacitor
switch SW1 is connected to one end of a resistor R. Another end of
the resistor R is connected to another end of the electronic
oscillator 210. By switching the capacitor switch SW1, only one of
the capacitors C0 to C4 is connected to the resistor. The frequency
of the oscillator is based on the RC value so that different
assembly of R and C will cause the oscillator to generate different
oscillation frequency. The capacitor switch SW1 is further
connected to the oscillation controlling processor 300. The
oscillation controlling processor 300 is built with a frequency
control software which includes the logics for controlling the
switching of the capacitor switch SW1 based on a desired effect of
the HID lamp. Furthermore, the present invention provides a
function for manually adjusting output frequencies of the
electronic oscillator to get a desired effect.
[0054] The second way of the present invention is illustrated in
FIG. 16, in that, one end of the electronic oscillator 210 is
connected with one end of a capacitor C. Another end of the
capacitor C is further connected to one end of a resistor switch
SW2. Another end of the resistor switch SW2 is connected to
respective ends of a plurality of resistors R0 to R4 which are
arranged in parallel. Another ends of the resistors R0 to R4 are
connected to another end of the electronic oscillator 210. By
switching the resistor switch SW2, the capacitor C is only
connected to one of the resistors R0 to R1 so as to change the
oscillation frequency of the electronic oscillator 210. The
resistor switch SW2 is connected to the oscillation controlling
processor 300. The oscillation controlling processor 300 is built
with a frequency control software which includes the logics for
controlling the switching of the capacitor switch SW1 based on a
desired effect of the HID lamp. Furthermore, the present invention
provides a function for manually adjusting output frequencies of
the electronic oscillator to get a desired effect.
[0055] The third way is illustrated in FIG. 17. One end of the
electronic oscillator 210 is connected to a capacitor switch SW1.
The capacitor switch SW1 is further connected to respective ends of
a plurality of capacitors C0 to C4. The capacitor switch SW1 cause
that only one of the capacitors C0 to C4 is conducted, while other
capacitors are disconnected in the circuit. Another ends of the
capacitors C0 to C4 are further connected to one end of a resistor
switch SW2 in parallel. Another end of the resistor switch SW2 is
connected to one ends of a plurality of resistors R0 to R4. Another
ends of the resistors R0 to R4 are connected to another end of the
electronic oscillator 210. The resistor switch SW2 causes that only
one of the resistors R0 to R4 is conducted, while other resistors
are not conducted. Thus the combinations of the capacitors C0 to C4
and the resistors R0 to R4 generate many different oscillation
frequencies to be provided by the electronic oscillator 210. The
capacitor switch SW1 and the resistor switch SW2 are connected to
the oscillation controlling processor 300. The oscillation
controlling processor 300 is built with a frequency control
software which includes the logics for controlling the switching of
the capacitor switch SW1 based on a desired effect of the HID lamp.
Furthermore, the present invention provides a function for manually
adjusting output frequencies of the electronic oscillator to get a
desired effect.
[0056] In the present invention, the oscillation controlling
processor 300 is an MCU, a FPGA/CPLD, or other logic circuit.
[0057] Referring to FIG. 18, in another way of the present
invention, the frequency controllable oscillator 200 is a quartz
oscillator 400 and a frequency controller 401. The quartz
oscillator 400 outputs a signal of fixed frequency which is further
input to the frequency controller 401. The frequency controller 400
can input the fixed frequency signal from the quartz oscillator 400
and output another signal with a desired frequency. The frequency
controller 401 is connected to the oscillation controlling
processor 402 and the PWM controller 100.
[0058] The oscillation controlling processor 402 is built with a
frequency control software which includes the logics for
controlling the frequency controller 401 based on a desired effect
of the HID lamp. Furthermore, the present invention provides a
function for manually adjusting output frequencies of the
electronic oscillator to get a desired effect.
[0059] From above analyze, it is known that the present invention
provides a frequency control function to the buck DC-DC converter
of an HID lamp so that change the illumination of the HID lamp.
[0060] Therefore, it only needs to add the structure of the present
invention to the original HID lamp. The illumination of the HID
lamp is changeable. Thus, the present invention is also made as an
illumination controller.
[0061] The above mentioned functions are achieved by modifying the
internal firmware in the processor of the lamp controller. Thus the
application is flexible.
[0062] It should be noted here, in dimming control, the HID lamp
has a preheat period of about 5 to 15 minutes after once the HID
lamp is started. The dimming control is performed after this time
period. Furthermore, the preheat period is varied based on the
manufacturers. Thus the controller (based on power or illumination)
initiates the dimming control after the preheat period (that is,
the HID lamp is in full power operation), while this is performed
based on the manufacturers.
[0063] Advantages of the present invention are that: The structure
of the ballast of the HID lamp is unnecessary to be modified. The
power of the ballast is used directly.
[0064] The present invention is thus described, it will be obvious
that the same may be varied in many ways. Such variations are not
to be regarded as a departure from the spirit and scope of the
present invention, and all such modifications as would be obvious
to one skilled in the art are intended to be included within the
scope of the following claims.
* * * * *